1. Field of the Invention
The present invention relates to an electromagnetic wave shield case disposed to cover electronic parts on a circuit board (printed circuit board) used for a cellular phone and a computer, and an electromagnetic wave shield case manufacturing method.
2. Description of the Related Art
When electronic parts such as an oscillator for generating electromagnetic waves are present on a circuit board, preventing influence on other circuit devices due to electromagnetic waves is required.
Specifically, in order to prevent occurrence of radiation noise, technologies have been identified that shielding the electronic parts so as not to propagate generated electromagnetic waves to the outside by surrounding the electronic parts with an electromagnetic wave shield case essentially made of metallic materials, which are of a conductive substance.
When such an electromagnetic wave shield case (hereinafter referred to as “shield case” when appropriate) is located on the circuit board, as shown in FIG. 1, a metallic ground line 3 (portion conducted to the earth (“grounding conduction portion”, hereinafter)) is provided in a region on a circuit board 1 corresponding to the lowermost portion of a shield case 50A and around it. The metallic ground line 3, and the lowermost portion of the shield case 50A, or part of the lowermost portion thereof are joined by soldering, and a soldering joint portion 4 is formed.
However, joining of the shield case 50A to the metallic ground line 3 by soldering has the following problems. That is, in a solder joining method, the following problems can be enumerated:
(a) adverse affects, which include deformation and partial breakage of the printed circuit board and electronic parts due to heating when soldering;
(b) an inefficient job of removing soldering from the shield case 50A when the shield case 50A on the circuit board 1 is used as a recycled product after its validity has expired;
(c) a troublesome job of performing treatments such as washing before and after the soldering is performed;
(d) fluxes, dispersal of soldering, and sticking of dispersed soldering on circuit elements at the stage of soldering; and
(e) the necessity to remove the soldering and detach the shield case 50A when electronic parts within the shield case 50A are replaced. Accordingly, various technologies have been heretofore proposed. Prior Art #1 solves the problem (e), and according to the Prior Art #1, as shown in FIG. 2, a truss-shaped frame 5 is joined to the metallic ground line 3 by soldering, and a so called two-piece type shield case 50B in which the truss-shaped frame 5 and a detachable upper cover 60 are combined.
Prior Art #2, which was developed by the Inventors of this application, solves the problems (a) to (e), whereby a shield case, in which an anchor pin integrally united thereto without soldering and has bending elasticity, is elastically joined to a through hole provided in a circuit board (for example, Japanese Patent Application Laid-open No. 2003-179378).
Prior Art #3 was also developed by the Inventors of this application to solve the problems (a) to (e). According to Prior Art #3, a lock pin having bending elasticity, which is integrally united with a back surface of a shield case without soldering, is elastically jointed to a housing for a circuit board. In Prior Art #3, a structure, in which part of the lowermost end of the shield case is made conductive by allowing the part to contact with a metallic ground line, is adopted (for example, Japanese Patent Application Laid-open No. 2003-179379).
Zr group amorphous alloy (metallic glass) having high amorphous forming ability as well as high strength and ductility, which has been developed by the Inventors of this application, has also been known (for example, Japanese Patent Application Laid-open Nos. 2000-129378 and 2000-178700).